1. Field of the Invention
The present invention relates to a belt unit used in an electrophotographic or electrostatic-recording image forming apparatus such as a copying machine, a printer, or a facsimile, and the image forming apparatus.
2. Description of the Related Art
For example, conventional electrophotographic image forming apparatuses use endless belts (each also referred to simply as a “belt” below) as a photosensitive belt, a transfer material conveying belt, an intermediate transfer belt, and the like. These belts may be damaged due to aging or fatigue attributable to many hours of driving, and hence require periodic replacement in many cases.
As a method of replacing such a belt, Japanese Patent Laid-Open No. 2004-109267 discloses the following. Specifically, a support unit that supports rollers around which a belt is stretched is formed so as to be foldable into two. To replace the belt, the support unit is folded so that the projected area defined by the outer-edge line of the support unit is smaller than that defined by the outer periphery of the belt when viewed from the side-surface side. In a different method, a support unit is formed of a pair of separable frames. To replace a belt, the frames are separated by unscrewing screws, and a roller is detached.
However, the above-described conventional methods often require a complex configuration and complicated operation for attaching and detaching the belt, which may cause damage to the belt during replacement of the belt.